Final Straw

: : What does the phrase mean - "that last mistake was the straw that broke the camel's back?"

:
: It derives, I believe, from a proverbial story, in which a camel was increasingly laden - finally it was a mere straw which proved too much for the poor beast to bear, and it broke its back.

: It has come to mean that in many cases, it will something seemingly very minor which proves too much to tolerate.

: DFG

It is a handy way of describing thresholds of tolerence - for example; if a person already has a high level of frustration - which can have physiological effects - adding something minor to that can raise the person's level into rage. I have often have to explain that to people trying to deal with stress/anger situations and it can help some people to see that they need to work on their underlying stresses to avoid that 'final straw' tipping them into rage.

it is a very useful metaphor for drawing attention to the fact that breaking point can be incrementally reached.